1. Field of the Invention
The present invention is directed in general to the field of semiconductor manufacturing. In one aspect, the present invention relates to the equipment for use in chemical mechanical polishing (CMP) in the manufacture of integrated circuits.
2. Description of the Related Art
In the manufacture of integrated circuits on semiconductor wafers, various layers are formed over one another, resulting in irregular or non-planar surface topologies. At any given stage in the fabrication of an integrated circuit, the non-planar surfaces can adversely affect subsequent processing steps, can lead to device failure and can reduce yield rates. For example, when metal lines are formed over a semiconductor structure, any non-planar surfaces can impede the ability to remove metal from the structure where it does not belong.
A common process for smoothing surface irregularities is through chemical mechanical planarization or chemical mechanical polishing (CMP). This process typically involves pressing a semiconductor wafer against a polishing pad at a controlled pressure, where either or both of the wafer and pad are rotating with respect to one another. With CMP equipment, the polishing pad typically includes a pressure sensitive adhesive layer which is used to affix the pad to a supporting platen structure. By spinning the polishing pad while the semiconductor wafer is pressed against the polishing pad in the presence of a chemically active or abrasive material or liquid media (slurry), the upper surface of the semiconductor wafer is planarized. The extent of polishing may be measured with laser interferometry or light reflectance techniques which use in-situ monitoring sensors located in the polishing pad or supporting platen assembly.
To allow light from the polishing environment at the wafer surface to be reflected back and measured, aperture windows in the polishing pad (referred to as the pad endpoint window) and in the platen assembly (referred to as the platen endpoint window) are aligned to allow light to pass from a laser or light source in the platen, to the wafer surface being polished and back to a sensor in the platen. However, during polish operations, air pressure builds up in the cavity that exists between the pad endpoint window and the platen endpoint window, which can cause bulging of the polishing pad endpoint window. Such bulges in the pad endpoint window create non-uniformities on the polished surface, and can cause the pad to breakthrough or slip/break wafers during the polishing process. In addition, any deformation of the pad endpoint window can introduce error to the endpoint signal that is used to stop polish operations, which in turn can cause wafers to be scrapped. Moreover, any bulging of the pad endpoint window can create excessive and/or localized wear of the pad endpoint window material. While prior attempts have been made to improve endpoint detection accuracy by providing a stable slurry or fluid environment at the wafer surface polish region, such solutions failed to prevent the fluid from entering between a platen window and pad window, which can adversely affect adhesion between the pad and platen, and can impair endpoint signal reliability.
Accordingly, a need exists for an improved CMP equipment assembly that eliminates the entrapment of air between the platen endpoint window and the polishing pad endpoint window. In addition, there is a need to prevent infiltration of polishing fluids from entering between the polishing pad and platen. There is also a need for an improved apparatus and device to overcome the problems in the art, such as outlined above. Further limitations and disadvantages of conventional processes and technologies will become apparent to one of skill in the art after reviewing the remainder of the present application with reference to the drawings and detailed description which follow.
It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for purposes of promoting and improving clarity and understanding. Further, where considered appropriate, reference numerals have been repeated among the drawings to represent corresponding or analogous elements.